System and method for sensing shape of elongated instrument

ABSTRACT

An instrument system that includes an elongate body and an optical fiber is provided. The elongate body includes a first elongate portion having a hollow lumen and a second elongate portion adjacent to the first elongate portion. The optical fiber is located in the lumen of the first elongate portion and in the second elongate portion. The optical fiber has a strain sensor provided thereon. The lumen is adapted to allow the optical fiber to move in the lumen relative to the elongate body, and the second elongate portion is adapted to prohibit all movement of the optical fiber relative to the elongate body.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 12/507,727 filed on Jul. 22, 2009, which is a continuation of U.S.patent application Ser. No. 11/690,116, filed on Mar. 22, 2007, whichclaims benefit under 35 U.S.C. §119 to U.S. provisional patentapplication Ser. Nos. 60/785,001, filed Mar. 22, 2006, and 60/788,176,filed Mar. 31, 2006. The foregoing applications are each herebyincorporated by reference into the present application in theirentirety.

FIELD OF INVENTION

The invention relates generally to medical instruments, such as elongatesteerable instruments for minimally-invasive intervention or diagnosis,and more particularly to a method, system, and apparatus for sensing ormeasuring the position and/or temperature at one or more distalpositions along the elongate steerable medical instrument.

BACKGROUND

Currently known minimally invasive procedures for diagnosis andtreatment of medical conditions use elongate instruments, such ascatheters or more rigid arms or shafts, to approach and address varioustissue structures within the body. For various reasons, it is highlyvaluable to be able to determine the 3-dimensional spatial position ofportions of such elongate instruments relative to other structures, suchas the operating table, other instruments, or pertinent tissuestructures. It is also valuable to be able to detect temperature atvarious locations of the instrument. Conventional technologies such aselectromagnetic position sensors, available from providers such as theBiosense Webster division of Johnson & Johnson, Inc., or conventionalthermocouples, available from providers such as Keithley Instruments,Inc., may be utilized to measure 3-dimensional spatial position ortemperature, respectively, but may be limited in utility for elongatemedical instrument applications due to hardware geometric constraints,electromagnetivity issues, etc.

There is a need for an alternative technology to facilitate theexecution of minimally-invasive interventional or diagnostic procedureswhile monitoring 3-dimensional spatial position and/or temperature.

It is well known that by applying the Bragg equation(wavelength=2*d*sin(theta)) to detect wavelength changes in reflectedlight, elongation in a diffraction grating pattern positionedlongitudinally along a fiber or other elongate structure may bedetermined. Further, with knowledge of thermal expansion properties offibers or other structures which carry a diffraction grating pattern,temperature readings at the site of the diffraction grating may becalculated.

So-called “Fiberoptic Bragg Grating” (“FBG”) sensors or componentsthereof, available from suppliers such as Luna Innovations, Inc., ofBlacksburg, Va., Micron Optics, Inc., of Atlanta, Ga., LxSix Photonics,Inc., of Quebec, Canada, and Ibsen Photonics A/S, of Denmark, have beenused in various applications to measure strain in structures such ashighway bridges and aircraft wings, and temperatures in structures suchas supply cabinets. An objective of this invention is to measure strainand/or temperature at distal portions of a steerable catheter or otherelongate medical instrument to assist in the performance of a medicaldiagnostic or interventional procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be readily understood by the followingdetailed description, taken in conjunction with accompanying drawings,illustrating by way of examples the principles of the presentdisclosure. The drawings illustrate the design and utility of preferredembodiments of the present disclosure, in which like elements arereferred to by like reference symbols or numerals. The objects andelements in the drawings are not necessarily drawn to scale, proportionor precise positional relationship; instead emphasis is focused onillustrating the principles of the present disclosure.

FIG. 1 illustrates an example of an elongate instrument such as aconventional manually operated catheter.

FIG. 2 illustrates another example of an elongate instrument such as arobotically-driven steerable catheter.

FIGS. 3A-3C illustrate implementations of an optical fiber with Bragggratings to an elongate instrument such as a robotically-steerablecatheter.

FIGS. 4A-4D illustrate implementations of an optical fiber with Bragggratings to an elongate instrument such as a robotically-steerablecatheter.

FIGS. 5A-D illustrate implementation of an optical fiber with Bragggratings to an elongate instrument as a robotically-steerable catheter.

FIG. 6 illustrates a cross sectional view of an elongate instrument suchas a catheter including an optical fiber with Bragg gratings.

FIG. 7 illustrates a cross sectional view of an elongate instrument suchas a catheter including a multi-fiber Bragg grating configuration.

FIG. 8 illustrates a cross sectional view of an elongate instrument suchas a catheter including a multi-fiber Bragg grating configuration.

FIGS. 9A-9B illustrate top and cross sectional views of an elongateinstrument such as a catheter having a multi-fiber structure with Bragggratings.

FIGS. 10A-10B illustrate top and cross sectional views of an elongateinstrument such as a catheter having a multi-fiber structure with Bragggratings.

FIGS. 11A-11B illustrate top and cross sectional views of an elongateinstrument such as a catheter having a multi-fiber structure with Bragggratings.

FIGS. 12A-12H illustrate cross sectional views of elongate instrumentswith various fiber positions and configurations.

FIG. 13 illustrates an optical fiber sensing system with Bragg gratings.

FIGS. 14A-14B illustrates an optical fiber sensing system with Bragggratings.

FIGS. 15A-15B illustrate optical fiber sensing system configurationswith Bragg gratings.

FIGS. 16A-16D illustrates integration of an optical fiber sensing systemto a robotically-controlled guide catheter configuration.

FIGS. 17A-17G illustrate integration of an optical fiber sensing systemto a robotically-controlled sheath catheter configuration.

FIG. 18 illustrates a cross sectional view of a bundle of optical fiberwithin the working lumen of a catheter.

FIG. 19 illustrates a robotic surgical system in accordance with someembodiments.

FIG. 20 illustrates an isometric view of an instrument having a guidecatheter in accordance with some embodiments.

FIG. 21 illustrates an isometric view of the instrument of FIG. 20,showing the instrument coupled to a sheath instrument in accordance withsome embodiments.

FIG. 22 illustrates an isometric view of a set of instruments for usewith an instrument driver in accordance with some embodiments.

FIG. 23 illustrates an isometric view of an instrument driver coupledwith a steerable guide instrument and a steerable sheath instrument inaccordance with some embodiments.

FIG. 24 illustrates components of the instrument driver of FIG. 23 inaccordance with some embodiments.

FIG. 25 illustrates the instrument driver of FIG. 24, showing theinstrument driver having a roll motor.

FIG. 26 illustrates components of an instrument driver in accordancewith some embodiments, showing the instrument driver having four motors.

FIG. 27 illustrates an operator control station in accordance with someembodiments.

FIG. 28A illustrates a master input device in accordance with someembodiments.

FIG. 28B illustrates a master input device in accordance with otherembodiments.

FIGS. 29-32 illustrate kinematics of a catheter in accordance withvarious embodiments.

FIGS. 33A-33E illustrates different bending configurations of a catheterin accordance with various embodiments.

FIG. 34 illustrates a control system in accordance with someembodiments.

FIG. 35A illustrates a localization sensing system having anelectromagnetic field receiver in accordance with some embodiments.

FIG. 35B illustrates a localization sensing system in accordance withother embodiments.

FIG. 36 illustrates a user interface for a master input device inaccordance with some embodiments.

FIGS. 37-47 illustrate software control schema in accordance withvarious embodiments.

FIG. 48 illustrates forward kinematics and inverse kinematics inaccordance with some embodiments.

FIG. 49 illustrates task coordinates, joint coordinates, and actuationcoordinates in accordance with some embodiments.

FIG. 50 illustrates variables associated with a geometry of a catheterin accordance with some embodiments.

FIG. 51 illustrates a block diagram of a system having a haptic masterinput device.

FIG. 52 illustrates a method for generating a haptic signal inaccordance with some embodiments.

FIG. 53 illustrates a method for converting an operator hand motion to acatheter motion in accordance with some embodiments.

SUMMARY OF THE INVENTION

In one embodiment of the present disclosure, an instrument system thatincludes an elongate body and an optical fiber is provided. The elongatebody includes a first elongate portion having a hollow lumen and asecond elongate portion adjacent to the first elongate portion. Theoptical fiber is located in the lumen of the first elongate portion andin the second elongate portion. The optical fiber has a strain sensorprovided thereon. The lumen is adapted to allow the optical fiber tomove in the lumen relative to the elongate body, and the second elongateportion is adapted to prohibit all movement of the optical fiberrelative to the elongate body.

In another embodiment of the present disclosure, an instrument systemthat includes an elongate body and a plurality of optical fibers isprovided. The elongate body has a plurality of hollow lumens that areeach offset from a neutral axis of the elongate body, wherein theplurality of hollow lumens form a triangular rosette in a cross sectionof the elongate body. Each optical fiber is at least partiallyencapsulated by one of the plurality of hollow lumens and has a strainsensor provided thereon.

These and other aspects of the present disclosure, as well as themethods of operation and functions of the related elements of structureand the combination of parts and economies of manufacture, will becomemore apparent upon consideration of the following description and theappended claims with reference to the accompanying drawings, all ofwhich form a part of this specification, wherein like reference numeralsdesignate corresponding parts in the various figures. In one embodiment,the structural components illustrated can be considered are drawn toscale. It is to be expressly understood, however, that the drawings arefor the purpose of illustration and description only and are notintended as a definition of the limits of the present disclosure. Itshall also be appreciated that the features of one embodiment disclosedherein can be used in other embodiments disclosed herein. As used in thespecification and in the claims, the singular form of “a”, “an”, and“the” include plural referents unless the context clearly dictatesotherwise.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring to FIG. 1, a conventional manually-steerable catheter (1) isdepicted. Pullwires (2) may be selectively tensioned throughmanipulation of a handle (3) on the proximal portion of the catheterstructure to make a more flexible distal portion (5) of the catheterbend or steer controllably. The handle (3) may be coupled, rotatably orslidably, for example, to a proximal catheter structure (34) which maybe configured to be held in the hand, and may be coupled to the elongateportion (35) of the catheter (1). A more proximal, and conventionallyless steerable, portion (4) of the catheter may be configured to becompliant to loads from surrounding tissues (for example, to facilitatepassing the catheter, including portions of the proximal portion,through tortuous pathways such as those formed by the blood vessels),yet less steerable as compared with the distal portion (5).

Referring to FIG. 2, a robotically-driven steerable catheter (6),similar to those described in detail in U.S. patent application Ser. No.11/176,598, incorporated by reference herein in its entirety, isdepicted. This catheter (6) has some similarities with themanually-steerable catheter (1) of FIG. 1 in that it has pullwires (10)associated distally with a more flexible section (8) configured to steeror bend when the pullwires (10) are tensioned in various configurations,as compared with a less steerable proximal portion (7) configured to bestiffer and more resistant to bending or steering. The depictedembodiment of the robotically-driven steerable catheter (6) comprisesproximal axles or spindles (9) configured to primarily interface notwith fingers or the hand, but with an electromechanical instrumentdriver configured to coordinate and drive, with the help of a computer,each of the spindles (9) to produce precise steering or bending movementof the catheter (6). The spindles (9) may be rotatably coupled to aproximal catheter structure (32) which may be configured to mount to anelectromechanical instrument driver apparatus, such as that described inthe aforementioned U.S. patent application Ser. No. 11/176,598, and maybe coupled to the elongate portion (33) of the catheter (6).

Each of the embodiments depicted in FIGS. 1 and 2 may have a workinglumen (not shown) located, for example, down the central axis of thecatheter body, or may be without such a working lumen. If a workinglumen is formed by the catheter structure, it may extend directly outthe distal end of the catheter, or may be capped or blocked by thedistal tip of the catheter. It is highly useful in many procedures tohave precise information regarding the position of the distal tip ofsuch catheters or other elongate instruments, such as those availablefrom suppliers such as the Ethicon Endosurgery division of Johnson &Johnson, or Intuitive Surgical Corporation. The examples andillustrations that follow are made in reference to arobotically-steerable catheter such as that depicted in FIG. 2, but aswould be apparent to one skilled in the art, the same principles may beapplied to other elongate instruments, such as the manually-steerablecatheter depicted in FIG. 1, or other elongate instruments, highlyflexible or not, from suppliers such as the Ethicon Endosurgery divisionof Johnson & Johnson, Inc., or Intuitive Surgical, Inc.

Referring to FIGS. 3A-3C, a robotically-steerable catheter (6) isdepicted having an optical fiber (12) positioned along one aspect of thewall of the catheter (6). The fiber is not positioned coaxially with theneutral axis of bending (11) in the bending scenarios depicted in FIGS.3B and 3C. Indeed, with the fiber (12) attached to, or longitudinallyconstrained by, at least two different points along the length of thecatheter (6) body (33) and unloaded from a tensile perspective relativeto the catheter body in a neutral position of the catheter body (33)such as that depicted in FIG. 3A, the longitudinally constrained portionof the fiber (12) would be placed in tension in the scenario depicted inFIG. 3B, while the longitudinally constrained portion of the fiber (12)would be placed in compression in the scenario depicted in FIG. 3C. Suchrelationships are elementary to solid mechanics, but may be applied asdescribed herein with the use of a Bragg fiber grating to assist in thedetermination of temperature and/or defection of an elongate instrument.Referring to FIGS. 4A-5D, several different embodiments are depicted.Referring to FIG. 4A, a robotic catheter (6) is depicted having a fiber(12) deployed through a lumen (31) which extends from the distal tip ofthe distal portion (8) of the catheter body (33) to the proximal end ofthe proximal catheter structure (32). In one embodiment a broadbandreference reflector (not shown) is positioned near the proximal end ofthe fiber in an operable relationship with the fiber Bragg gratingwherein an optical path length is established for each reflector/gratingrelationship comprising the subject fiber Bragg sensor configuration;additionally, such configuration also comprises a reflectometer (notshown), such as a frequency domain reflectometer, to conduct spectralanalysis of detected reflected portions of light waves.

Constraints (30) may be provided to prohibit axial or longitudinalmotion of the fiber (12) at the location of each constraint (30).Alternatively, the constraints (30) may only constrain the position ofthe fiber (12) relative to the lumen (31) in the location of theconstraints (30). For example, in one variation of the embodimentdepicted in FIG. 4A, the most distal constraint (30) may be configuredto disallow longitudinal or axial movement of the fiber (12) relative tothe catheter body (33) at the location of such constraint (30), whilethe more proximal constraint (30) may merely act as a guide to lift thefiber (12) away from the walls of the lumen (31) at the location of suchproximal constraint (30). In another variation of the embodimentdepicted in FIG. 4A, both the more proximal and more distal constraints(30) may be configured to disallow longitudinal or axial movement of thefiber (12) at the locations of such constraints, and so on. As shown inthe embodiment depicted in FIG. 4A, the lumen (31) in the region of theproximal catheter structure (32) is without constraints to allow forfree longitudinal or axial motion of the fiber relative to the proximalcatheter structure (32). Constraints configured to prohibit relativemotion between the constraint and fiber at a given location may comprisesmall adhesive or polymeric welds, interference fits formed with smallgeometric members comprising materials such as polymers or metals,locations wherein braiding structures are configured with extratightness to prohibit motion of the fiber, or the like. Constraintsconfigured to guide the fiber (12) but to also allow relativelongitudinal or axial motion of the fiber (12) relative to suchconstraint may comprise small blocks, spheres, hemispheres, etc.defining small holes, generally through the geometric middle of suchstructures, for passage of the subject fiber (12).

The embodiment of FIG. 4B is similar to that of FIG. 4A, with theexception that there are two additional constraints (30) provided toguide and/or prohibit longitudinal or axial movement of the fiber (12)relative to such constraints at these locations. In one variation, eachof the constraints is a total relative motion constraint, to isolate thelongitudinal strain within each of three “cells” provided by isolatingthe length of the fiber (12) along the catheter body (33) into threesegments utilizing the constraints (30). In another variation of theembodiment depicted in FIG. 4B, the proximal and distal constraints (30)may be total relative motion constraints, while the two intermediaryconstraints (30) may be guide constraints configured to allowlongitudinal or axial relative motion between the fiber (12) and suchconstraints at these intermediary locations, but to keep the fiberaligned near the center of the lumen (31) at these locations.

Referring to FIG. 4C, an embodiment similar to those of FIGS. 4A and 4Bis depicted, with the exception that entire length of the fiber thatruns through the catheter body (33) is constrained by virtue of beingsubstantially encapsulated by the materials which comprise the catheterbody (33). In other words, while the embodiment of FIG. 4C does have alumen (31) to allow free motion of the fiber (12) longitudinally oraxially relative to the proximal catheter structure (32), there is nosuch lumen defined to allow such motion along the catheter body (33),with the exception of the space naturally occupied by the fiber as itextends longitudinally through the catheter body (33) materials whichencapsulate it.

FIG. 4D depicts a configuration similar to that of FIG. 4C with theexception that the lumen (31) extends not only through the proximalcatheter structure (32), but also through the proximal portion (7) ofthe catheter body (33); the distal portion of the fiber (12) which runsthrough the distal portion of the catheter body (33) is substantiallyencapsulated and constrained by the materials which comprise thecatheter body (33).

FIGS. 5A-5D depict embodiments analogous to those depicted in FIGS.4A-D, with the exception that the fiber (12) is positioned substantiallyalong the neutral axis of bending (11) of the catheter body (33), and inthe embodiment of FIG. 5B, there are seven constraints (30) as opposedto the three of the embodiment in FIG. 4B.

Referring to FIG. 6, a cross section of a portion of the catheter body(33) of the configuration depicted in FIG. 4C is depicted, to clearlyillustrate that the fiber (12) is not placed concentrically with theneutral axis (11) of bending for the sample cross section. FIG. 7depicts a similar embodiment, wherein a multi-fiber bundle (13), such asthose available from Luna Technologies, Inc., is positioned within thewall of the catheter rather than a single fiber as depicted in FIG. 6,the fiber bundle (13) comprising multiple, in this embodiment three,individual (e.g., smaller) fibers or fiber cores (14). When a structuresuch as that depicted in FIG. 7 is placed in bending in a configurationsuch as that depicted in FIG. 3B or 3C, the most radially outward (fromthe neutral axis of bending (11)) of the individual fibers (14)experiences more compression or tension than the more radially inwardfibers. Alternatively, in an embodiment such as that depicted in FIG. 8,which shows a cross section of the catheter body (33) portion aconfiguration such as that depicted in FIG. 5C, a multi-fiber bundle(13) is positioned coaxially with the neutral axis of bending (11) forthe catheter (6), and each of three individual fibers (14) within thebundle (13) will experience different degrees of tension and/orcompression in accordance with the bending or steering configuration ofthe subject catheter, as would be apparent to one skilled in the art.For example, referring to FIGS. 9A and 9B (a cross section), at aneutral position, all three individual fibers (14) comprising thedepicted bundle (13) may be in an unloaded configuration. With downwardbending, as depicted in FIGS. 10A and 10B (a cross section), thelowermost two fibers comprising the bundle (13) may be configured toexperience compression, while the uppermost fiber experiences tension.The opposite would happen with an upward bending scenario such as thatdepicted in FIGS. 11A and 11B (cross section).

Indeed, various configurations may be employed, depending upon theparticular application, such as those depicted in FIGS. 12A-12H. Forsimplicity, each of the cross sectional embodiments of FIGS. 12A-12H isdepicted without reference to lumens adjacent the fibers, or constraints(i.e., each of the embodiments of FIGS. 12A-12H are depicted inreference to catheter body configurations analogous to those depicted,for example, in FIGS. 4C and 5C, wherein the fibers are substantiallyencapsulated by the materials comprising the catheter body (33);additional variations comprising combinations and permutations ofconstraints and constraining structures, such as those depicted in FIGS.4A-5D, are within the scope of this invention. FIG. 12A depicts anembodiment having one fiber (12). FIG. 12B depicts a variation havingtwo fibers (12) in a configuration capable of detecting tensionssufficient to calculate three-dimensional spatial deflection of thecatheter portion. FIG. 12C depicts a two-fiber variation with what maybe considered redundancy for detecting bending about a bending axis suchas that depicted in FIG. 12C. FIGS. 12D and 12E depict three-fiberconfigurations configured for detecting three-dimensional spatialdeflection of the subject catheter portion. FIG. 12F depicts a variationhaving four fibers configured to accurately detect three-dimensionalspatial deflection of the subject catheter portion. FIGS. 12G and 12Hdepict embodiments similar to 12B and 12E, respectively, with theexception that multiple bundles of fibers are integrated, as opposed tohaving a single fiber in each location. Each of the embodiments depictedin FIGS. 12A-12H, each of which depicts a cross section of an elongateinstrument comprising at least one optical fiber, may be utilized tofacilitate the determination of bending deflection, torsion, compressionor tension, and/or temperature of an elongate instrument. Suchrelationships may be clarified in reference to FIGS. 13, 14A, and 14B.

In essence, the 3-dimensional position of an elongate member may bedetermined by determining the incremental curvature experienced alongvarious longitudinal sections of such elongate member. In other words,if you know how much an elongate member has curved in space at severalpoints longitudinally down the length of the elongate member, you candetermine the position of the distal portion and more proximal portionsin three-dimensional space by virtue of the knowing that the sectionsare connected, and where they are longitudinally relative to each other.Towards this end, variations of embodiments such as those depicted inFIGS. 12A-12H may be utilized to determine the position of a catheter orother elongate instrument in 3-dimensional space. To determine localcurvatures at various longitudinal locations along an elongateinstrument, fiber optic Bragg grating analysis may be utilized.

Referring to FIG. 13, a single optical fiber (12) is depicted havingfour sets of Bragg diffraction gratings, each of which may be utilizedas a local deflection sensor. Such a fiber (12) may be interfaced withportions of an elongate instrument, as depicted, for example, in FIGS.12A-12H. A single detector (15) may be utilized to detect and analyzesignals from more than one fiber. With a multi-fiber configuration, suchas those depicted in FIGS. 12B-12H, a proximal manifold structure may beutilized to interface the various fibers with one or more detectors.Interfacing techniques for transmitting signals between detectors andfibers are well known in the art of optical data transmission. Thedetector is operatively coupled with a controller configured todetermine a geometric configuration of the optical fiber and, therefore,at least a portion of the associated elongate instrument (e.g.,catheter) body based on a spectral analysis of the detected reflectedlight signals. Further details are provided in Published US PatentApplication 2006/0013523, the contents of which are fully incorporatedherein by reference.

In the single fiber embodiment depicted in FIG. 13, each of thediffraction gratings has a different spacing (d1, d2, d3, d4), and thusa proximal light source for the depicted single fiber and detector maydetect variations in wavelength for each of the “sensor” lengths (L10,L20, L30, L40). Thus, given determined length changes at each of the“sensor” lengths (L10, L20, L30, L40), the longitudinal positions of the“sensor” lengths (L10, L20, L30, L40), and a known configuration such asthose depicted in cross section in FIGS. 12A-12H, the deflection and/orposition of the associated elongate instrument in space may bedetermined. One of the challenges with a configuration such as thatdepicted in FIG. 13 is that a fairly broad band emitter and broad bandtunable detector must be utilized proximally to capture lengthdifferentiation data from each of the sensor lengths, potentiallycompromising the number of sensor lengths that may be monitored, etc.Regardless, several fiber (12) and detector (15) configurations such asthat depicted in FIG. 13 may comprise embodiments such as those depictedin FIGS. 12A-12H to facilitate determination of three-dimensionalpositioning of an elongate medical instrument.

In another embodiment of a single sensing fiber, depicted in FIG. 14A,various sensor lengths (L50, L60, L70, L80) may be configured to eachhave the same grating spacing, and a more narrow band source may beutilized with some sophisticated analysis, as described, for example, in“Sensing Shape—Fiber-Bragg-grating sensor arrays monitor shape at highresolution,” SPIE's OE Magazine, September, 2005, pages 18-21,incorporated by reference herein in its entirety, to monitor elongationat each of the sensor lengths given the fact that such sensor lengthsare positioned at different positions longitudinally (L1, L2, L3, L4)away from the proximal detector (15). In another (related) embodiment,depicted in FIG. 14B, a portion of a given fiber, such as the distalportion, may have constant gratings created to facilitatehigh-resolution detection of distal lengthening or shortening of thefiber. Such a constant grating configuration would also be possible withthe configurations described in the aforementioned scientific journalarticle.

Referring to FIGS. 15A and 15B, temperature may be sensed utilizingFiber-Bragg grating sensing in embodiments similar to those depicted inFIGS. 13 and 14A-B. Referring to FIG. 15A, a single fiber protrudesbeyond the distal tip of the depicted catheter (6) and is unconstrained,or at least less constrained, relative to other surrounding structuresso that the portion of the depicted fiber is free to change in lengthwith changes in temperature. With knowledge of the thermal expansion andcontraction qualities of the small protruding fiber portion, and one ormore Bragg diffraction gratings in such protruding portion, the changesin length may be used to extrapolate changes in temperature and thus beutilized for temperature sensing. Referring to FIG. 15B, a small cavity(21) or lumen may be formed in the distal portion of the catheter body(33) to facilitate free movement of the distal portion (22) of the fiber(12) within such cavity (21) to facilitate temperature sensing distallywithout the protruding fiber depicted in FIG. 15A.

As will be apparent to those skilled in the art, the fibers in theembodiments depicted herein will provide accurate measurements oflocalized length changes in portions of the associated catheter orelongate instrument only if such fiber portions are indeed coupled insome manner to the nearby portions of the catheter or elongateinstrument. In one embodiment, it is desirable to have the fiber orfibers intimately coupled with or constrained by the surroundinginstrument body along the entire length of the instrument, with theexception that one or more fibers may also be utilized to sensetemperature distally, and may have an unconstrained portion, as in thetwo scenarios described in reference to FIGS. 15A and 15B. In oneembodiment, for example, each of several deflection-sensing fibers mayterminate in a temperature sensing portion, to facilitate positiondetermination and highly localized temperature sensing and comparison atdifferent aspects of the distal tip of an elongate instrument. Inanother embodiment, the proximal portions of the fiber(s) in the lessbendable catheter sections are freely floating within the catheter body,and the more distal/bendable fiber portions intimately coupled, tofacilitate high-precision monitoring of the bending within the distal,more flexible portion of the catheter or elongate instrument.

Referring to FIGS. 16A, 16B, and 16D, a catheter-like robotic guideinstrument integration embodiment is depicted. U.S. patent applicationSer. No. 11/176,598, from which these drawings (along with FIGS. 17 and18) have been taken and modified, is incorporated herein by reference inits entirety. FIGS. 16A and 16B show an embodiment with three opticalfibers (12) and a detector (15) for detecting catheter bending anddistal tip position. FIG. 16C depicts and embodiment having four opticalfibers (12) for detecting catheter position. FIG. 16D depicts anintegration to build such embodiments. As shown in FIG. 16D, in step“E+”, mandrels for optical fibers are woven into a braid layer,subsequent to which (step “F”) Bragg-grated optical fibers arepositioned in the cross sectional space previously occupied by suchmandrels (after such mandrels are removed). The geometry of the mandrelsrelative to the fibers selected to occupy the positions previouslyoccupied by the mandrels after the mandrels are removed preferably isselected based upon the level of constraint desired between the fibers(12) and surrounding catheter body (33) materials. For example, if ahighly-constrained relationship, comprising substantial encapsulation,is desired, the mandrels will closely approximate the size of thefibers. If a more loosely-constrained geometric relationship is desired,the mandrels may be sized up to allow for relative motion between thefibers (12) and the catheter body (33) at selected locations, or atubular member, such as a polyimide or PTFE sleeve, may be insertedsubsequent to removal of the mandrel, to provide a “tunnel” withclearance for relative motion of the fiber, and/or simply a layer ofprotection between the fiber and the materials surrounding it whichcomprise the catheter or instrument body (33). Similar principles may beapplied in embodiments such as those described in reference to FIGS.17A-17G.

Referring to FIGS. 17A-F, two sheath instrument integrations aredepicted, each comprising a single optical fiber (12). FIG. 17G depictsan integration to build such embodiments. As shown in FIG. 16D, in step“B”, a mandrel for the optical fiber is placed, subsequent to which(step “K”) a Bragg-grated optical fiber is positioned in the crosssectional space previously occupied by the mandrel (after such mandrelis removed).

Referring to FIG. 18, in another embodiment, a bundle (13) of fibers(14) may be placed down the working lumen of an off-the-shelf roboticcatheter (guide or sheath instrument type) such as that depicted in FIG.18, and coupled to the catheter in one or more locations, with aselected level of geometric constraint, as described above, to provide3-D spatial detection.

Tension and compression loads on an elongate instrument may be detectedwith common mode deflection in radially-outwardly positioned fibers, orwith a single fiber along the neutral bending axis. Torque may bedetected by sensing common mode additional tension (in addition, forexample, to tension and/or compression sensed by, for example, a singlefiber coaxial with the neutral bending axis) in outwardly-positionedfibers in configurations such as those depicted in FIGS. 12A-H.

In another embodiment, the tension elements utilized to actuate bending,steering, and/or compression of an elongate instrument, such as asteerable catheter, may comprise optical fibers with Bragg gratings, ascompared with more conventional metal wires or other structures, andthese fiber optic tension elements may be monitored for deflection asthey are loaded to induce bending/steering to the instrument. Suchmonitoring may be used to prevent overstraining of the tension elements,and may also be utilized to detect the position of the instrument as awhole, as per the description above.

Referring to FIG. 19, one embodiment of a robotic catheter system 32,includes an operator control station 2 located remotely from anoperating table 22, to which an instrument driver 16 and instrument 18are coupled by an instrument driver mounting brace 20. A communicationlink 14 transfers signals between the operator control station 2 andinstrument driver 16. The instrument driver mounting brace 20 of thedepicted embodiment is a relatively simple, arcuate-shaped structuralmember configured to position the instrument driver 16 above a patient(not shown) lying on the table 22.

FIGS. 20 and 21 depict isometric views of respective embodiments ofinstruments configured for use with an embodiment of the instrumentdriver (16), such as that depicted in FIG. 19. FIG. 20 depicts aninstrument (18) embodiment without an associated coaxial sheath coupledat its midsection. FIG. 21 depicts a set of two instruments (28),combining an embodiment like that of FIG. 20 with a coaxially coupledand independently controllable sheath instrument (30). To distinguishthe non-sheath instrument (18) from the sheath instrument (30) in thecontext of this disclosure, the “non-sheath” instrument may also betermed the “guide” instrument (18).

Referring to FIG. 22, a set of instruments (28), such as those in FIG.21, is depicted adjacent an instrument driver (16) to illustrate anexemplary mounting scheme. The sheath instrument (30) may be coupled tothe depicted instrument driver (16) at a sheath instrument interfacesurface (38) having two mounting pins (42) and one interface socket (44)by sliding the sheath instrument base (46) over the pins (42).Similarly, and preferably simultaneously, the guide instrument (18) base(48) may be positioned upon the guide instrument interface surface (40)by aligning the two mounting pins (42) with alignment holes in the guideinstrument base (48). As will be appreciated, further steps may berequired to lock the instruments (18, 30) into place upon the instrumentdriver (16).

In FIG. 23, an instrument driver (16) is depicted as interfaced with asteerable guide instrument (18) and a steerable sheath instrument (30).FIG. 24 depicts an embodiment of the instrument driver (16), in whichthe sheath instrument interface surface (38) remains stationary, andrequires only a simple motor actuation in order for a sheath to besteered using an interfaced control element via a control elementinterface assembly (132). This may be accomplished with a simple cableloop about a sheath socket drive pulley (272) and a capstan pulley (notshown), which is fastened to a motor, similar to the two upper motors(242) (visible in FIG. 24). The drive motor for the sheath socket driveschema is hidden under the linear bearing interface assembly.

The drive schema for the four guide instrument interface sockets (270)is more complicated, due in part to the fact that they are coupled to acarriage (240) configured to move linearly along a linear bearinginterface (250) to provide for motor-driven insertion of a guideinstrument toward the patient relative to the instrument driver,hospital table, and sheath instrument. Various conventional cabletermination and routing techniques are utilized to accomplish apreferably high-density instrument driver structure with the carriage(240) mounted forward of the motors for a lower profile patient-sideinterface.

Still referring to FIG. 24, the instrument driver (16) is rotatablymounted to an instrument driver base (274), which is configured tointerface with an instrument driver mounting brace (not shown), such asthat depicted in FIG. 19, or a movable setup joint construct (notshown). Rotation between the instrument driver base (274) and aninstrument driver base plate (276) to which it is coupled is facilitatedby a heavy-duty flanged bearing structure (278). The flanged bearingstructure (278) is configured to allow rotation of the body of theinstrument driver (16) about an axis approximately coincident with thelongitudinal axis of a guide instrument (not shown) when the guideinstrument is mounted upon the instrument driver (16) in a neutralposition. This rotation preferably is automated or powered by a rollmotor (280) and a simple roll cable loop (286), which extends aroundportions of the instrument driver base plate and terminates as depicted(282, 284). Alternatively, roll rotation may be manually actuated andlocked into place with a conventional clamping mechanism. The roll motor(280) position is more easily visible in FIG. 25.

FIG. 26 illustrates another embodiment of an instrument driver,including a group of four motors (290). Each motor (290) has anassociated high-precision encoder for controls purposes and beingconfigured to drive one of the four guide instrument interface sockets(270), at one end of the instrument driver. Another group of two motors(one hidden, one visible—288) with encoders (292) are configured todrive insertion of the carriage (240) and the sheath instrumentinterface socket (268).

Referring to FIG. 27, an operator control station is depicted showing acontrol button console (8), a computer (6), a computer control interface(10), such as a mouse, a visual display system (4) and a master inputdevice (12). In addition to “buttons” on the button console (8)footswitches and other known user control interfaces may be utilized toprovide an operator interface with the system controls.

Referring to FIG. 28A, in one embodiment, the master input device (12)is a multi-degree-of-freedom device having multiple joints andassociated encoders (306). An operator interface (217) is configured forcomfortable interfacing with the human fingers. The depicted embodimentof the operator interface (217) is substantially spherical. Further, themaster input device may have integrated haptics capability for providingtactile feedback to the user.

Another embodiment of a master input device (12) is depicted in FIG. 28Bhaving a similarly-shaped operator interface (217). Suitable masterinput devices are available from manufacturers such as Sensible DevicesCorporation under the trade name “Phanto®”, or Force Dimension under thetrade name “Omega®”. In one embodiment featuring an Omega-type masterinput device, the motors of the master input device are utilized forgravity compensation. In other words, when the operator lets go of themaster input device with his hands, the master input device isconfigured to stay in position, or hover around the point at which itwas left, or another predetermined point, without gravity taking thehandle of the master input device to the portion of the master inputdevice's range of motion closest to the center of the earth. In anotherembodiment, haptic feedback is utilized to provide feedback to theoperator that he has reached the limits of the pertinent instrumentworkspace. In another embodiment, haptic feedback is utilized to providefeedback to the operator that he has reached the limits of the subjecttissue workspace when such workspace has been registered to theworkspace of the instrument (i.e., should the operator be navigating atool such as an ablation tip with a guide instrument through a 3-D modelof a heart imported, for example, from CT data of an actual heart, themaster input device is configured to provide haptic feedback to theoperator that he has reached a wall or other structure of the heart asper the data of the 3-D model, and therefore help prevent the operatorfrom driving the tool through such wall or structure without at leastfeeling the wall or structure through the master input device). Inanother embodiment, contact sensing technologies configured to detectcontact between an instrument and tissue may be utilized in conjunctionwith the haptic capability of the master input device to signal theoperator that the instrument is indeed in contact with tissue.

Referring to FIGS. 29-32, the basic kinematics of a catheter with fourcontrol elements is reviewed.

Referring to FIGS. 29A-B, as tension is placed only upon the bottomcontrol element (312), the catheter bends downward, as shown in FIG.29A. Similarly, pulling the left control element (314) in FIGS. 30A-Bbends the catheter left, pulling the right control element (310) inFIGS. 31A-B bends the catheter right, and pulling the top controlelement (308) in FIGS. 32A-B bends the catheter up. As will be apparentto those skilled in the art, well-known combinations of applied tensionabout the various control elements results in a variety of bendingconfigurations at the tip of the catheter member (90). One of thechallenges in accurately controlling a catheter or similar elongatemember with tension control elements is the retention of tension incontrol elements, which may not be the subject of the majority of thetension loading applied in a particular desired bending configuration.If a system or instrument is controlled with various levels of tension,then losing tension, or having a control element in a slackconfiguration, can result in an unfavorable control scenario.

Referring to FIGS. 33A-E, a simple scenario is useful in demonstratingthis notion. As shown in FIG. 33A, a simple catheter (316) steered withtwo control elements (314, 310) is depicted in a neutral position. Ifthe left control element (314) is placed into tension greater than thetension, if any, which the right control element (310) experiences, thecatheter (316) bends to the left, as shown in FIG. 33B. If a change ofdirection is desired, this paradigm needs to reverse, and the tension inthe right control element (310) needs to overcome that in the leftcontrol element (314). At the point of a reversal of direction likethis, where the tension balance changes from left to right, withoutslack or tension control, the right most control element (314) maygather slack which needs to be taken up before precise control can bereestablished. Subsequent to a “reeling in” of slack which may bepresent, the catheter (316) may be may be pulled in the oppositedirection, as depicted in FIGS. 33C-E, without another slack issue froma controls perspective until a subsequent change in direction.

The above-described instrument embodiments present various techniquesfor managing tension control in various guide instrument systems havingbetween two and four control elements.

For example, in one set of embodiments, tension may be controlled withactive independent tensioning of each control element in the pertinentguide catheter via independent control element interface assemblies(132) associated with independently-controlled guide instrumentinterface sockets (270) on the instrument driver (16). Thus, tension maybe managed by independently actuating each of the control elementinterface assemblies (132) in a four-control-element embodiment, athree-control-element embodiment, or a two-control-element embodiment.

In another set of embodiments, tension may be controlled with activeindependent tensioning with a split carriage design. For example, asplit carriage with two independent linearly movable portions, may beutilized to actively and independently tension each of the two controlelement interface assemblies (132), each of which is associated with twodimensions of a given degree of freedom. For example, there can be + and−pitch on one interface assembly, + and −yaw on the other interfaceassembly, with slack or tension control provided for pitch by one of thelinearly movable portions (302) of the split carriage (296), and slackor tension control provided for yaw by the other linearly movableportion (302) of the split carriage (296).

Similarly, slack or tension control for a single degree of freedom, suchas yaw or pitch, may be provided by a single-sided split carriagedesign, with the exception that only one linearly movable portion wouldbe required to actively tension the single control element interfaceassembly of an instrument.

In another set of embodiments, tensioning may be controlled withspring-loaded idlers configured to keep the associated control elementsout of slack. The control elements preferably are pre-tensioned in eachembodiment to prevent slack and provide predictable performance. Indeed,in yet another set of embodiments, pre-tensioning may form the mainsource of tension management. In the case of embodiments only havingpre-tensioning or spring-loaded idler tensioning, the control system mayneed to be configured to reel in bits of slack at certain transitionpoints in catheter bending, such as described above in relation to FIGS.33A and 33B.

To accurately coordinate and control actuations of various motors withinan instrument driver from a remote operator control station such as thatdepicted in FIG. 19, an advanced computerized control and visualizationsystem is preferred. While the control system embodiments that followare described in reference to a particular control systems interface,namely the SimuLink® and XPC® control interfaces available from TheMathworks Inc., and PC-based computerized hardware configurations, manyother configurations may be utilized, including various pieces ofspecialized hardware, in place of more flexible software controlsrunning on PC-based systems.

Referring to FIG. 34, an overview of an embodiment of a controls systemflow is depicted. A master computer (400) running master input devicesoftware, visualization software, instrument localization software, andsoftware to interface with operator control station buttons and/orswitches is depicted. In one embodiment, the master input devicesoftware is a proprietary module packaged with an off-the-shelf masterinput device system, such as the Phantom® from Sensible DevicesCorporation, which is configured to communicate with the Phantom®hardware at a relatively high frequency as prescribed by themanufacturer. Other suitable master input devices, such as that (12)depicted in FIG. 28B are available from suppliers such as ForceDimension of Lausanne, Switzerland. The master input device (12) mayalso have haptics capability to facilitate feedback to the operator, andthe software modules pertinent to such functionality may also beoperated on the master computer (400). Preferred embodiments of hapticsfeedback to the operator are discussed in further detail below.

The term “localization” is used in the art in reference to systems fordetermining and/or monitoring the position of objects, such as medicalinstruments, in a reference coordinate system. In one embodiment, theinstrument localization software is a proprietary module packaged withan off-the-shelf or custom instrument position tracking system, such asthose available from Ascension Technology Corporation, Biosense Webster,Inc, Endocardial Solutions, Inc., Boston Scientific (EP Technologies),Medtronic, Inc., and others. Such systems may be capable of providingnot only real-time or near real-time positional information, such asX-Y-Z coordinates in a Cartesian coordinate system, but also orientationinformation relative to a given coordinate axis or system. Some of thecommercially-available localization systems use electromagneticrelationships to determine position and/or orientation, while others,such as some of those available from Endocardial Solutions, Inc.—St JudeMedical, utilize potential difference or voltage, as measured between aconductive sensor located on the pertinent instrument and conductiveportions of sets of patches placed against the skin, to determineposition and/or orientation. Referring to FIGS. 35A and 35B, variouslocalization sensing systems may be utilized with the variousembodiments of the robotic catheter system disclosed herein. In otherembodiments not comprising a localization system to determine theposition of various components, kinematic and/or geometric relationshipsbetween various components of the system may be utilized to predict theposition of one component relative to the position of another. Someembodiments may utilize both localization data and kinematic and/orgeometric relationships to determine the positions of variouscomponents.

As shown in FIG. 35A, one preferred localization system comprises anelectromagnetic field transmitter (406) and an electromagnetic fieldreceiver (402) positioned within the central lumen of a guide catheter(90). The transmitter (406) and receiver (402) are interfaced with acomputer operating software configured to detect the position of thedetector relative to the coordinate system of the transmitter (406) inreal or near-real time with high degrees of accuracy. Referring to FIG.35B, a similar embodiment is depicted with a receiver (404) embeddedwithin the guide catheter (90) construction. Preferred receiverstructures may comprise three or more sets of very small coils spatiallyconfigured to sense orthogonal aspects of magnetic fields emitted by atransmitter. Such coils may be embedded in a custom configuration withinor around the walls of a preferred catheter construct. For example, inone embodiment, two orthogonal coils are embedded within a thinpolymeric layer at two slightly flattened surfaces of a catheter (90)body approximately ninety degrees orthogonal to each other about thelongitudinal axis of the catheter (90) body, and a third coil isembedded in a slight polymer-encapsulated protrusion from the outside ofthe catheter (90) body, perpendicular to the other two coils. Due to thevery small size of the pertinent coils, the protrusion of the third coilmay be minimized Electronic leads for such coils may also be embedded inthe catheter wall, down the length of the catheter body to a position,preferably adjacent an instrument driver, where they may be routed awayfrom the instrument to a computer running localization software andinterfaced with a pertinent transmitter.

In another similar embodiment (not shown), one or more conductive ringsmay be electronically connected to a potential-difference-basedlocalization/orientation system, along with multiple sets, preferablythree sets, of conductive skin patches, to provide localization and/ororientation data utilizing a system such as those available fromEndocardial Solutions—St. Jude Medical. The one or more conductive ringsmay be integrated into the walls of the instrument at variouslongitudinal locations along the instrument, or set of instruments. Forexample, a guide instrument may have several conductive ringslongitudinally displaced from each other toward the distal end of theguide instrument, while a coaxially-coupled sheath instrument maysimilarly have one or more conductive rings longitudinally displacedfrom each other toward the distal end of the sheath instrument—toprovide precise data regarding the location and/or orientation of thedistal ends of each of such instruments.

Referring back to FIG. 34, in one embodiment, visualization softwareruns on the master computer (400) to facilitate real-time driving andnavigation of one or more steerable instruments. In one embodiment,visualization software provides an operator at an operator controlstation, such as that depicted in FIG. 19 (2), with a digitized“dashboard” or “windshield” display to enhance instinctive drivabilityof the pertinent instrumentation within the pertinent tissue structures.Referring to FIG. 36, a simple illustration is useful to explain oneembodiment of a preferred relationship between visualization andnavigation with a master input device (12). In the depicted embodiment,two display views (410, 412) are shown. One preferably represents aprimary (410) navigation view, and one may represent a secondary (412)navigation view. To facilitate instinctive operation of the system, itis preferable to have the master input device coordinate system at leastapproximately synchronized with the coordinate system of at least one ofthe two views. Further, it is preferable to provide the operator withone or more secondary views which may be helpful in navigating throughchallenging tissue structure pathways and geometries.

Using the operation of an automobile as an example, if the master inputdevice is a steering wheel and the operator desires to drive a car in aforward direction using one or more views, his first priority is likelyto have a view straight out the windshield, as opposed to a view out theback window, out one of the side windows, or from a car in front of thecar that he is operating. The operator might prefer to have the forwardwindshield view as his primary display view, such that a right turn onthe steering wheel takes him right as he observes his primary display, aleft turn on the steering wheel takes him left, and so forth. If theoperator of the automobile is trying to park the car adjacent anothercar parked directly in front of him, it might be preferable to also havea view from a camera positioned, for example, upon the sidewalk aimedperpendicularly through the space between the two cars (one driven bythe operator and one parked in front of the driven car), so the operatorcan see the gap closing between his car and the car in front of him ashe parks. While the driver might not prefer to have to completelyoperate his vehicle with the sidewalk perpendicular camera view as hissole visualization for navigation purposes, this view is helpful as asecondary view.

Referring still to FIG. 36, if an operator is attempting to navigate asteerable catheter in order to, for example, contact a particular tissuelocation with the catheter's distal tip, a useful primary navigationview (410) may comprise a three dimensional digital model of thepertinent tissue structures (414) through which the operator isnavigating the catheter with the master input device (12), along with arepresentation of the catheter distal tip location (416) as viewed alongthe longitudinal axis of the catheter near the distal tip. Thisembodiment illustrates a representation of a targeted tissue structurelocation (418), which may be desired in addition to the tissue digitalmodel (414) information. A useful secondary view (412), displayed upon adifferent monitor, in a different window upon the same monitor, orwithin the same user interface window, for example, comprises anorthogonal view depicting the catheter tip representation (416), andalso perhaps a catheter body representation (420), to facilitate theoperator's driving of the catheter tip toward the desired targetedtissue location (418).

In one embodiment, subsequent to development and display of a digitalmodel of pertinent tissue structures, an operator may select one primaryand at least one secondary view to facilitate navigation of theinstrumentation. By selecting which view is a primary view, the user canautomatically toggle a master input device (12) coordinate system tosynchronize with the selected primary view. In an embodiment with theleftmost depicted view (410) selected as the primary view, to navigatetoward the targeted tissue site (418), the operator should manipulatethe master input device (12) forward, to the right, and down. The rightview will provide valued navigation information, but will not be asinstinctive from a “driving” perspective.

To illustrate: if the operator wishes to insert the catheter tip towardthe targeted tissue site (418) watching only the rightmost view (412)without the master input device (12) coordinate system synchronized withsuch view, the operator would have to remember that pushing straightahead on the master input device will make the distal tip representation(416) move to the right on the rightmost display (412). Should theoperator decide to toggle the system to use the rightmost view (412) asthe primary navigation view, the coordinate system of the master inputdevice (12) is then synchronized with that of the rightmost view (412),enabling the operator to move the catheter tip (416) closer to thedesired targeted tissue location (418) by manipulating the master inputdevice (12) down and to the right.

The synchronization of coordinate systems described herein may beconducted using fairly conventional mathematic relationships. Forexample, in one embodiment, the orientation of the distal tip of thecatheter may be measured using a 6-axis position sensor system such asthose available from Ascension Technology Corporation, Biosense Webster,Inc., Endocardial Solutions, Inc., Boston Scientific (EP Technologies),and others. A 3-axis coordinate frame, C, for locating the distal tip ofthe catheter, is constructed from this orientation information. Theorientation information is used to construct the homogeneoustransformation matrix, T_(Gref) ^(G0), which transforms a vector in theCatheter coordinate frame “C” to the fixed Global coordinate frame “G”in which the sensor measurements are done (the subscript G_(ref) andsuperscript C_(ref) are used to represent the O'th, or initial, step).As a registration step, the computer graphics view of the catheter isrotated until the master input and the computer graphics view of thecatheter distal tip motion are coordinated and aligned with the cameraview of the graphics scene. The 3-axis coordinate frame transformationmatrix T_(Gref) ^(G0) for the camera position of this initial view isstored (subscripts G_(ref) and superscript C_(ref) stand for the globaland camera “reference” views). The corresponding catheter “referenceview” matrix for the catheter coordinates is obtained as:

T _(Cref) ^(C0) =T _(G0) ^(C0) T _(Gref) ^(G0) T _(Cref) ^(Gref)=(T_(C0) ^(G0))⁻¹ T _(Gref) ^(G0) T _(C1) ^(G1)

Also note that the catheter's coordinate frame is fixed in the globalreference frame G, thus the transformation matrix between the globalframe and the catheter frame is the same in all views, i.e., T_(C0)^(G0)=T_(Cref) ^(Gref)=T_(Ci) ^(Gi) for any arbitrary view i. Thecoordination between primary view and master input device coordinatesystems is achieved by transforming the master input as follows: Givenany arbitrary computer graphics view of the representation, e.g. thei'th view, the 3-axis coordinate frame transformation matrix T_(Gi)^(G0) of the camera view of the computer graphics scene is obtained fromthe computer graphics software.

The corresponding catheter transformation matrix is computed in asimilar manner as above:

T _(Ci) ^(C0) =T _(G0) ^(C0) T _(G) ^(G0) T _(Ci) ^(Gi)=(T _(C0)^(G0))⁻¹ T _(Gi) ^(G0) T _(Ci) ^(Gi)

The transformation that needs to be applied to the master input whichachieves the view coordination is the one that transforms from thereference view that was registered above, to the current ith view, i.e.,T_(Cref) ^(Ci). Using the previously computed quantities above, thistransform is computed as:

T _(Cref) ^(Ci) =T _(C0) ^(Ci) T _(Cref) ^(C0)

The master input is transformed into the commanded catheter input byapplication of the transformation T_(Cref) ^(Ci). Given a command input

${r_{master} = \begin{bmatrix}x_{master} \\y_{master} \\y_{master}\end{bmatrix}},$

-   -   one may calculate:

$r_{catheter} = {\begin{bmatrix}x_{catheter} \\y_{catheter} \\y_{catheter}\end{bmatrix} = {{T_{Cref}^{Ci}\begin{bmatrix}x_{master} \\y_{master} \\y_{master}\end{bmatrix}}.}}$

Under such relationships, coordinate systems of the primary view andmaster input device may be aligned for instinctive operation.

Referring back to embodiment of FIG. 34, the master computer (400) alsocomprises software and hardware interfaces to operator control stationbuttons, switches, and other input devices which may be utilized, forexample, to “freeze” the system by functionally disengaging the masterinput device as a controls input, or provide toggling between variousscaling ratios desired by the operator for manipulated inputs at themaster input device (12). The master computer (400) has two separatefunctional connections with the control and instrument driver computer(422): one (426) for passing controls and visualization relatedcommands, such as desired XYZ (in the catheter coordinate system)commands, and one (428) for passing safety signal commands. Similarly,the control and instrument driver computer (422) has two separatefunctional connections with the instrument and instrument driverhardware (424): one (430) for passing control and visualization relatedcommands such as required-torque-related voltages to the amplifiers todrive the motors and encoders, and one (432) for passing safety signalcommands.

In one embodiment, the safety signal commands represent a simple signalrepeated at very short intervals, such as every 10 milliseconds, suchsignal chain being logically read as “system is ok, amplifiers stayactive”. If there is any interruption in the safety signal chain, theamplifiers are logically toggled to inactive status and the instrumentcannot be moved by the control system until the safety signal chain isrestored. Also shown in the signal flow overview of FIG. 34 is a pathway(434) between the physical instrument and instrument driver hardwareback to the master computer to depict a closed loop system embodimentwherein instrument localization technology, such as that described inreference to FIGS. 35A-B, is utilized to determine the actual positionof the instrument to minimize navigation and control error, as describedin further detail below.

FIGS. 37-47 depict various aspects of one embodiment of a SimuLink®software control schema for an embodiment of the physical system, withparticular attention to an embodiment of a “master following mode.” Inthis embodiment, an instrument is driven by following instructions froma master input device, and a motor servo loop embodiment, whichcomprises key operational functionality for executing upon commandsdelivered from the master following mode to actuate the instrument.

FIG. 37 depicts a high-level view of an embodiment wherein any one ofthree modes may be toggled to operate the primary servo loop (436). Inidle mode (438), the default mode when the system is started up, all ofthe motors are commanded via the motor servo loop (436) to servo abouttheir current positions, their positions being monitored with digitalencoders associated with the motors. In other words, idle mode (438)deactivates the motors, while the remaining system stays active. Thus,when the operator leaves idle mode, the system knows the position of therelative components. In auto home mode (440), cable loops within anassociated instrument driver, such as that depicted in FIG. 23, arecentered within their cable loop range to ensure substantiallyequivalent range of motion of an associated instrument in bothdirections for a various degree of freedom, such as + and −directions ofpitch or yaw, when loaded upon the instrument driver. This is a setupmode for preparing an instrument driver before an instrument is engaged.

In master following mode (442), the control system receives signals fromthe master input device, and in a closed loop embodiment from both amaster input device and a localization system, and forwards drivesignals to the primary servo loop (436) to actuate the instrument inaccordance with the forwarded commands. Aspects of this embodiment ofthe master following mode (442) are depicted in further detail in FIGS.42-124. Aspects of the primary servo loop and motor servo block (444)are depicted in further detail in FIGS. 38-41.

Referring to FIG. 42, a more detailed functional diagram of anembodiment of master following mode (442) is depicted. As shown in FIG.42, the inputs to functional block (446) are XYZ position of the masterinput device in the coordinate system of the master input device which,per a setting in the software of the master input device may be alignedto have the same coordinate system as the catheter, and localization XYZposition of the distal tip of the instrument as measured by thelocalization system in the same coordinate system as the master inputdevice and catheter. Referring to FIG. 43 for a more detailed view offunctional block (446) of FIG. 42, a switch (460) is provided at blockto allow switching between master inputs for desired catheter position,to an input interface (462) through which an operator may command thatthe instrument go to a particular XYZ location in space. Variouscontrols features may also utilize this interface to provide an operatorwith, for example, a menu of destinations to which the system shouldautomatically drive an instrument, etc. Also depicted in FIG. 43 is amaster scaling functional block (451) which is utilized to scale theinputs coming from the master input device with a ratio selectable bythe operator. The command switch (460) functionality includes a low passfilter to weight commands switching between the master input device andthe input interface (462), to ensure a smooth transition between thesemodes.

Referring back to FIG. 42, desired position data in XYZ terms is passedto the inverse kinematics block (450) for conversion to pitch, yaw, andextension (or “insertion”) terms in accordance with the predictedmechanics of materials relationships inherent in the mechanical designof the instrument.

The kinematic relationships for many catheter instrument embodiments maybe modeled by applying conventional mechanics relationships. In summary,a control-element-steered catheter instrument is controlled through aset of actuated inputs. In a four-control-element catheter instrument,for example, there are two degrees of motion actuation, pitch and yaw,which both have + and −directions. Other motorized tension relationshipsmay drive other instruments, active tensioning, or insertion or roll ofthe catheter instrument. The relationship between actuated inputs andthe catheter's end point position as a function of the actuated inputsis referred to as the “kinematics” of the catheter.

Referring to FIG. 48, the “forward kinematics” expresses the catheter'send-point position as a function of the actuated inputs while the“inverse kinematics” expresses the actuated inputs as a function of thedesired end-point position. Accurate mathematical models of the forwardand inverse kinematics are essential for the control of a roboticallycontrolled catheter system. For clarity, the kinematics equations arefurther refined to separate out common elements, as shown in FIG. 48.The basic kinematics describes the relationship between the taskcoordinates and the joint coordinates. In such case, the taskcoordinates refer to the position of the catheter end-point while thejoint coordinates refer to the bending (pitch and yaw, for example) andlength of the active catheter. The actuator kinematics describes therelationship between the actuation coordinates and the jointcoordinates. The task, joint, and bending actuation coordinates for therobotic catheter are illustrated in FIG. 49. By describing thekinematics in this way we can separate out the kinematics associatedwith the catheter structure, namely the basic kinematics, from thoseassociated with the actuation methodology.

The development of the catheter's kinematics model is derived using afew essential assumptions. Included are assumptions that the catheterstructure is approximated as a simple beam in bending from a mechanicsperspective, and that control elements, such as thin tension wires,remain at a fixed distance from the neutral axis and thus impart auniform moment along the length of the catheter.

In addition to the above assumptions, the geometry and variables shownin FIG. 50 are used in the derivation of the forward and inversekinematics. The basic forward kinematics, relating the catheter taskcoordinates (X_(c), Y_(c), Z_(c)) to the joint coordinates (φ_(pitch),φ_(yaw), L), is given as follows:

X _(c) =w cos(Θ)

Y _(c) =R sin(α)

Z _(c) =w sin(Θ)

-   -   Where        -   w=R(1−cos(α))        -   α=[(φ_(pitch))²+(φ_(yaw))²]^(1/2) (total bending)        -   R=L/α. (bend radius)        -   Θ=α tan 2(φ_(pitch), φ_(yaw)) (roll angle)

The actuator forward kinematics, relating the joint coordinates(φ_(pitch), φ_(yaw), L) to the actuator coordinates (ΔL_(x), ΔL_(z), L)is given as follows:

φ_(pitch)=2ΔL _(z) /D _(c)

φ_(yaw)=2ΔL _(x) /D _(c)

As illustrated in FIG. 48, the catheter's end-point position can bepredicted given the joint or actuation coordinates by using the forwardkinematics equations described above.

Calculation of the catheter's actuated inputs as a function of end-pointposition, referred to as the inverse kinematics, can be performednumerically, using a nonlinear equation solver such as Newton-Raphson. Amore desirable approach, and the one used in this illustrativeembodiment, is to develop a closed-form solution which can be used tocalculate the required actuated inputs directly from the desiredend-point positions.

As with the forward kinematics, we separate the inverse kinematics intothe basic inverse kinematics, which relates joint coordinates to thetask coordinates, and the actuation inverse kinematics, which relatesthe actuation coordinates to the joint coordinates. The basic inversekinematics, relating the joint coordinates (φ_(pitch), φ_(yaw), L), tothe catheter task coordinates (X_(c), Y_(c), Z_(c)) is given as follows:

φ_(pitch) = α sin (θ) φ_(yaw) = α cos (θ)$L =  {R\; \alpha}arrow  {where}arrow arrow\begin{matrix}\overset{\_}{\theta = {\alpha \; \tan \; 2( {Z_{c},X_{c}} )}} & \overset{\_}{\beta = {\alpha \; \tan \; 2( {Y_{c},W_{c}} )}} \\{R =  \frac{l\; \sin \; \beta}{\sin \; 2\beta}arrow } & {W_{c} = ( {X_{c}^{2} + Z_{c}^{2}} )^{1/2}} \\{\alpha = {\pi - {2\beta}}} & \underset{\_}{l = ( {W_{c}^{2} + Y_{c}^{2}} )^{1/2}}\end{matrix}   $

The actuator inverse kinematics, relating the actuator coordinates(ΔL_(x), ΔL_(z), L) to the joint coordinates (φ_(pitch), φ_(yaw), L) isgiven as follows:

ΔL _(x) =D _(c)φ_(yaw)

ΔL _(z) =Dcφ _(pitch)

Referring back to FIG. 42, pitch, yaw, and extension commands are passedfrom the inverse kinematics (450) to a position control block (448)along with measured localization data. FIG. 47 provides a more detailedview of the position control block (448). After measured XYZ positiondata comes in from the localization system, it goes through an inversekinematics block (464) to calculate the pitch, yaw, and extension theinstrument needs to have in order to travel to where it needs to be.Comparing (466) these values with filtered desired pitch, yaw, andextension data from the master input device, integral compensation isthen conducted with limits on pitch and yaw to integrate away the error.In this embodiment, the extension variable does not have the same limits(468), as do pitch and yaw (470). As will be apparent to those skilledin the art, having an integrator in a negative feedback loop forces theerror to zero. Desired pitch, yaw, and extension commands are nextpassed through a catheter workspace limitation (452), which may be afunction of the experimentally determined physical limits of theinstrument beyond which componentry may fail, deform undesirably, orperform unpredictably or undesirably. This workspace limitationessentially defines a volume similar to a cardioid-shaped volume aboutthe distal end of the instrument. Desired pitch, yaw, and extensioncommands, limited by the workspace limitation block, are then passed toa catheter roll correction block (454).

This functional block is depicted in further detail in FIG. 44, andessentially comprises a rotation matrix for transforming the pitch, yaw,and extension commands about the longitudinal, or “roll”, axis of theinstrument—to calibrate the control system for rotational deflection atthe distal tip of the catheter that may change the control elementsteering dynamics. For example, if a catheter has no rotationaldeflection, pulling on a control element located directly up at twelveo'clock should urge the distal tip of the instrument upward. If,however, the distal tip of the catheter has been rotationally deflectedby, say, ninety degrees clockwise, to get an upward response from thecatheter, it may be necessary to tension the control element that wasoriginally positioned at a nine o'clock position. The catheter rollcorrection schema depicted in FIG. 44 provides a means for using arotation matrix to make such a transformation, subject to a rollcorrection angle, such as the ninety degrees in the above example, whichis input, passed through a low pass filter, turned to radians, and putthrough rotation matrix calculations.

In one embodiment, the roll correction angle is determined throughexperimental experience with a particular instrument and path ofnavigation. In another embodiment, the roll correction angle may bedetermined experimentally in-situ using the accurate orientation dataavailable from the preferred localization systems. In other words, withsuch an embodiment, a command to, for example, bend straight up can beexecuted, and a localization system can be utilized to determine atwhich angle the defection actually went—to simply determine the in-situroll correction angle.

Referring briefly back to FIG. 42, roll corrected pitch and yawcommands, as well as unaffected extension commands, are output from theroll correction block (454) and may optionally be passed to aconventional velocity limitation block (456). Referring to FIG. 45,pitch and yaw commands are converted from radians to degrees, andautomatically controlled roll may enter the controls picture to completethe current desired position (472) from the last servo cycle. Velocityis calculated by comparing the desired position from the previous servocycle, as calculated with a conventional memory block (476) calculation,with that of the incoming commanded cycle. A conventional saturationblock (474) keeps the calculated velocity within specified values, andthe velocity-limited command (478) is converted back to radians andpassed to a tension control block (458).

Tension within control elements may be managed depending upon theparticular instrument embodiment, as described above in reference to thevarious instrument embodiments and tension control mechanisms. As anexample, FIG. 46 depicts a pre-tensioning block (480) with which a givencontrol element tension is ramped to a present value. An adjustment isthen added to the original pre-tensioning based upon a preferablyexperimentally-tuned matrix pertinent to variables, such as the failurelimits of the instrument construct and the incoming velocity-limitedpitch, yaw, extension, and roll commands. This adjusted value is thenadded (482) to the original signal for output, via gear ratioadjustment, to calculate desired motor rotation commands for the variousmotors involved with the instrument movement. In this embodiment,extension, roll, and sheath instrument actuation (484) have nopre-tensioning algorithms associated with their control. The output isthen complete from the master following mode functionality, and thisoutput is passed to the primary servo loop (436).

Referring back to FIG. 37, incoming desired motor rotation commands fromeither the master following mode (442), auto home mode (440), or idlemode (438) in the depicted embodiment are fed into a motor servo block(444), which is depicted in greater detail in FIGS. 38-41.

Referring to FIG. 38, incoming measured motor rotation data from digitalencoders and incoming desired motor rotation commands are filtered usingconventional quantization noise filtration at frequencies selected foreach of the incoming data streams to reduce noise while not adding unduedelays which may affect the stability of the control system. As shown inFIGS. 40 and 41, conventional quantization filtration is utilized on themeasured motor rotation signals at about 200 hertz in this embodiment,and on the desired motor rotation command at about 15 hertz. Thedifference (488) between the quantization filtered values forms theposition error which may be passed through a lead filter, the functionalequivalent of a proportional derivative (“PD”)+low pass filter. Inanother embodiment, conventional PID, lead/lag, or state spacerepresentation filter may be utilized. The lead filter of the depictedembodiment is shown in further detail in FIG. 39.

In particular, the lead filter embodiment in FIG. 39 comprises a varietyof constants selected to tune the system to achieve desired performance.The depicted filter addresses the needs of one embodiment of a 4-controlelement guide catheter instrument with independent control of each offour control element interface assemblies for .+-.pitch and .+-.yaw, andseparate roll and extension control. As demonstrated in the depictedembodiment, insertion and roll have different inertia and dynamics asopposed to pitch and yaw controls, and the constants selected to tunethem is different. The filter constants may be theoretically calculatedusing conventional techniques and tuned by experimental techniques, orwholly determined by experimental techniques, such as setting theconstants to give a sixty degree or more phase margin for stability andspeed of response, a conventional phase margin value for medical controlsystems.

In an embodiment where a tuned master following mode is paired with atuned primary servo loop, an instrument and instrument driver, such asthose described above, may be “driven” accurately in three-dimensionswith a remotely located master input device. Other preferred embodimentsincorporate related functionalities, such as haptic feedback to theoperator, active tensioning with a split carriage instrument driver,navigation utilizing direct visualization and/or tissue models acquiredin-situ and tissue contact sensing, and enhanced navigation logic.

Referring to FIG. 51, in one embodiment, the master input device may bea haptic master input device, such as those available from SensibleDevices, Inc., under the trade name Phantom®, and the hardware andsoftware required for operating such a device may at least partiallyreside on the master computer. The master XYZ positions measured fromthe master joint rotations and forward kinematics are generally passedto the master computer via a parallel port or similar link and maysubsequently be passed to a control and instrument driver computer. Withsuch an embodiment, an internal servo loop for the Phantom® generallyruns at a much higher frequency in the range of 1,000 Hz, or greater, toaccurately create forces and torques at the joints of the master.

Referring to FIG. 52, a sample flowchart of a series of operationsleading from a position vector applied at the master input device to ahaptic signal applied back at the operator is depicted. A vector (344)associated with a master input device move by an operator may betransformed into an instrument coordinate system, and in particular to acatheter instrument tip coordinate system, using a simple matrixtransformation (345). The transformed vector (346) may then be scaled(347) per the preferences of the operator, to produce ascaled-transformed vector (348). The scaled-transformed vector (348) maybe sent to both the control and instrument driver computer (422)preferably via a serial wired connection, and to the master computer fora catheter workspace check (349) and any associated vector modification(350). this is followed by a feedback constant multiplication (351)chosen to produce preferred levels of feedback, such as force, in orderto produce a desired force vector (352), and an inverse transform (353)back to the master input device coordinate system for associated hapticsignaling to the operator in that coordinate system (354).

A conventional Jacobian may be utilized to convert a desired forcevector (352) to torques desirably applied at the various motorscomprising the master input device, to give the operator a desiredsignal pattern at the master input device. Given this embodiment of asuitable signal and execution pathway, feedback to the operator in theform of haptics, or touch sensations, may be utilized in various ways toprovide added safety and instinctiveness to the navigation features ofthe system, as discussed in further detail below.

FIG. 53 is a system block diagram including haptics capability. As shownin summary form in FIG. 53, encoder positions on the master inputdevice, changing in response to motion at the master input device, aremeasured (355), sent through forward kinematics calculations (356)pertinent to the master input device to get XYZ spatial positions of thedevice in the master input device coordinate system (357), thentransformed (358) to switch into the catheter coordinate system and(perhaps) transform for visualization orientation and preferred controlsorientation, to facilitate “instinctive driving.”

The transformed desired instrument position (359) may then be sent downone or more controls pathways to, for example, provide haptic feedback(360) regarding workspace boundaries or navigation issues, and provide acatheter instrument position control loop (361) with requisite catheterdesired position values, as transformed utilizing inverse kinematicsrelationships for the particular instrument (362) into yaw, pitch, andextension, or “insertion”, terms (363) pertinent to operating theparticular catheter instrument with open or closed loop control.

While multiple embodiments and variations of the many aspects of theinvention have been disclosed and described herein, such disclosure isprovided for purposes of illustration only. Many combinations andpermutations of the disclosed system are useful in minimally invasivemedical intervention and diagnosis, and the system is configured to beflexible. The foregoing illustrated and described embodiments of theinvention are susceptible to various modifications and alternativeforms, and it should be understood that the invention generally, as wellas the specific embodiments described herein, are not limited to theparticular forms or methods disclosed, but also cover all modifications,equivalents and alternatives falling within the scope of the appendedclaims. Further, the various features and aspects of the illustratedembodiments may be incorporated into other embodiments, even if no sodescribed herein, as will be apparent to those skilled in the art.

1. An instrument system, comprising: an elongate body comprising a firstelongate portion having a hollow lumen and a second elongate portionadjacent to the first elongate portion; and an optical fiber located inthe lumen of the first elongate portion and in the second elongateportion, the optical fiber having a strain sensor provided thereon,wherein the lumen is adapted to allow the optical fiber to move in thelumen relative to the elongate body, and wherein the second elongateportion is adapted to prohibit all movement of the optical fiberrelative to the elongate body.
 2. The instrument system of claim 1,wherein the optical fiber is embedded in material of the second elongateportion.
 3. The instrument system of claim 1, wherein the lumen has alongitudinal axis that is offset from a neutral axis of the elongatebody.
 4. The instrument system of claim 1, wherein the elongate bodycomprises a catheter and wherein the strain sensor comprises one or moreBragg gratings.
 5. An instrument system comprising: an elongate bodyhaving a plurality of hollow lumens that are each offset from a neutralaxis of the elongate body, wherein the plurality of hollow lumens form atriangular rosette in a cross section of the elongate body; and aplurality of optical fibers, each optical fiber being at least partiallyencapsulated by one of the plurality of hollow lumens and having astrain sensor provided thereon.
 6. The instrument system of claim 5,further comprising a lumen coaxial with the neutral axis of the elongatebody.